gas fireplace/oil heat best practices

Good day.
I've been following this group for a while now. I'm 25 and just bought
my first home last weekend. Ive been here a week now.
I have a gas fireplace downstairs in my den, and I have baseboard
heaters that run on oil.
I pay $2.60 a gal for the gas to run the fireplace
I pay $2.40 a gal for the oil.
My question is when should I use the gas fireplace in order to
maximize heat and minimize cost?
For example, if the gas fireplace uses less gas for the same about of
heat that I would get out of the baseboard heaters, then I'd imagine I
want to run the fireplace all day.
Also, I upgraded my manual thermostats to electronic programmable
themorostats. I leave it cold upstairs all day, and cold downstairs
all night. Around 62 degrees. Are these best practices?
Thank for the advice.
~ Mike

You're buying natural gas by the gallon? Isn't that kind of odd?
I'd expect it to be in cubic feet, or something. In any case,
I seriously doubt that the gas fireplace is putting heat into your
house more efficiently than the oil boiler, unless the gas fireplace
in unvented. If it's unvented, I'm pretty sure that the
operating instructions are that you shouldn't use it
unless you are present, sober, and awake.
Which means that you should use the oil heat for heating,
and limit the gas fireplace to decoration, and supplementary
heat when you're in the room it's in. This is convenient,
because the thermostats that you've just upgraded probably
aren't connected to the fireplace....
Personally, I'd put the setback for anytime nobody's in
the house all the way down to 50, and direct any further
energy-saving effort to finding and plugging air leaks,
and adding window coverings.
--Goedjn

Does the fireplace run on propane? That's the only "gas" fuel I can
think of that's delivered in liquid form.
Are the baseboard heaters hot water, fed from an oil-fired boiler, or
something else?

Answering that requires more information than you've provided. Here's
how you might go about it:
- Look up the energy content of the propane, in BTU/gal.
- Multiply by the efficiency of the fireplace to determine how many of
those BTUs end up in your house. This number can vary widely - some
fireplaces look pretty but send most of the heat up the chimney, while
others have a heat exchanger to put most of the heat into the room. The
result will be in useful BTU/gal.
- Divide by the fuel price to get useful BTU per dollar.
- Do the same calculation with oil. The efficiency of the system
depends on both the efficiency of the boiler and how much of the heat in
the water makes it into your rooms.
When you're done, you should know whether it's cheaper to get raw BTUs
from propane or oil. Then you have to take localization into account.
If you're in the room with the fireplace, it's likely cheaper to use the
fireplace to warm just than room than it is to use the boiler to warm
the whole house, because the fireplace *isn't* warming the whole house.
On the other hand, trying to use the fireplace to warm rooms other than
the one it is in is likely pointless. The fireplace just isn't going to
warm the whole house.
Dave

:
: Does the fireplace run on propane? That's the only "gas" fuel
I can
: think of that's delivered in liquid form.
CY:I think that's what he said in another post.
:
: Are the baseboard heaters hot water, fed from an oil-fired
boiler, or
: something else?
CY: Think that's it.
:
: >My question is when should I use the gas fireplace in order to
: >maximize heat and minimize cost?
:
: Answering that requires more information than you've provided.
Here's
: how you might go about it:
:
: - Look up the energy content of the propane, in BTU/gal.
CY: I had that figure awhile back. It's 21,500 BTU per pound.
:
: - Multiply by the efficiency of the fireplace to determine how
many of
: those BTUs end up in your house. This number can vary widely -
some
: fireplaces look pretty but send most of the heat up the
chimney, while
: others have a heat exchanger to put most of the heat into the
room. The
: result will be in useful BTU/gal.
CY: Figure about 0.80 is a good SWAG.
:
: - Divide by the fuel price to get useful BTU per dollar.
CY: I'd think you'd want to get the dollars per BTU. After all,
we price gasoline by $ per galon. Though, BTU per dollar is also
useful.
:
: - Do the same calculation with oil. The efficiency of the
system
: depends on both the efficiency of the boiler and how much of
the heat in
: the water makes it into your rooms.
CY: Fuel oil, I remember is about 140,000 BTU per galon.
:
: When you're done, you should know whether it's cheaper to get
raw BTUs
: from propane or oil. Then you have to take localization into
account.
: If you're in the room with the fireplace, it's likely cheaper
to use the
: fireplace to warm just than room than it is to use the boiler
to warm
: the whole house, because the fireplace *isn't* warming the
whole house.
: On the other hand, trying to use the fireplace to warm rooms
other than
: the one it is in is likely pointless. The fireplace just isn't
going to
: warm the whole house.
CY: Excellent advice.
:
: Dave

While it may be possible with a very efficient fireplace, it is very
unlikely that you can ever come out ahead using the fireplace for heat, even
if the propane was half the price.
I would not be surprised if using the fireplace actually cause increased
use of oil. The fireplace pulls in fresh (cold) air warms it and sends it
outside.

Some NG fireplaces vent into the living space. Those are 100%
efficient. I dunno if propane ones ever do that, or not.
(and for myself, the whole idea makes my skin crawl, but apparently
they don't kill people all that often...)

There is quite a variety of gas fireplaces. Some use room air for
combustion, some use outdoor air. Of the ones that use room air, ones
with sealed glass fronts may consume little air above what's needed for
combustion.
Our own house has a couple of 20,000 BTU/hr gas fires mounted in front
of old wood-burning fireplace boxes. The combustion (fire) chamber has
a sealed glass window, and there's a heat exchanger between the
fire chamber and the vent outlet, so much of the heat in the combustion
gases is used to heat room air. Combustion does use room air, and the
draft diverter hood pulls in a bit more room air, but not a lot.
I've checked the vent on the roof when the gas fire is full on, and the
exhaust gas flow is quite modest. The cap on the vent never gets too
hot to touch. When I compare that to the flow of hot air that stays
within the room with the fireplace, it's clear that the majority of the
heat from the fire stays in the room. And the room *does* get warmer.
It all depends on the fireplace design.
Dave

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